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Message-Id: <20200117205149.97262-1-lyude@redhat.com>
Date: Fri, 17 Jan 2020 15:51:49 -0500
From: Lyude Paul <lyude@...hat.com>
To: dri-devel@...ts.freedesktop.org
Cc: Sean Paul <sean@...rly.run>, Wayne Lin <Wayne.Lin@....com>,
Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Maxime Ripard <mripard@...nel.org>,
David Airlie <airlied@...ux.ie>,
Daniel Vetter <daniel@...ll.ch>, linux-kernel@...r.kernel.org
Subject: [PATCH] Revert "drm/dp_mst: Remove VCPI while disabling topology mgr"
This reverts commit 64e62bdf04ab8529f45ed0a85122c703035dec3a.
This commit ends up causing some lockdep splats due to trying to grab the
payload lock while holding the mgr's lock:
[ 54.010099]
[ 54.011765] ======================================================
[ 54.018670] WARNING: possible circular locking dependency detected
[ 54.025577] 5.5.0-rc6-02274-g77381c23ee63 #47 Not tainted
[ 54.031610] ------------------------------------------------------
[ 54.038516] kworker/1:6/1040 is trying to acquire lock:
[ 54.044354] ffff888272af3228 (&mgr->payload_lock){+.+.}, at:
drm_dp_mst_topology_mgr_set_mst+0x218/0x2e4
[ 54.054957]
[ 54.054957] but task is already holding lock:
[ 54.061473] ffff888272af3060 (&mgr->lock){+.+.}, at:
drm_dp_mst_topology_mgr_set_mst+0x3c/0x2e4
[ 54.071193]
[ 54.071193] which lock already depends on the new lock.
[ 54.071193]
[ 54.080334]
[ 54.080334] the existing dependency chain (in reverse order) is:
[ 54.088697]
[ 54.088697] -> #1 (&mgr->lock){+.+.}:
[ 54.094440] __mutex_lock+0xc3/0x498
[ 54.099015] drm_dp_mst_topology_get_port_validated+0x25/0x80
[ 54.106018] drm_dp_update_payload_part1+0xa2/0x2e2
[ 54.112051] intel_mst_pre_enable_dp+0x144/0x18f
[ 54.117791] intel_encoders_pre_enable+0x63/0x70
[ 54.123532] hsw_crtc_enable+0xa1/0x722
[ 54.128396] intel_update_crtc+0x50/0x194
[ 54.133455] skl_commit_modeset_enables+0x40c/0x540
[ 54.139485] intel_atomic_commit_tail+0x5f7/0x130d
[ 54.145418] intel_atomic_commit+0x2c8/0x2d8
[ 54.150770] drm_atomic_helper_set_config+0x5a/0x70
[ 54.156801] drm_mode_setcrtc+0x2ab/0x833
[ 54.161862] drm_ioctl+0x2e5/0x424
[ 54.166242] vfs_ioctl+0x21/0x2f
[ 54.170426] do_vfs_ioctl+0x5fb/0x61e
[ 54.175096] ksys_ioctl+0x55/0x75
[ 54.179377] __x64_sys_ioctl+0x1a/0x1e
[ 54.184146] do_syscall_64+0x5c/0x6d
[ 54.188721] entry_SYSCALL_64_after_hwframe+0x49/0xbe
[ 54.194946]
[ 54.194946] -> #0 (&mgr->payload_lock){+.+.}:
[ 54.201463]
[ 54.201463] other info that might help us debug this:
[ 54.201463]
[ 54.210410] Possible unsafe locking scenario:
[ 54.210410]
[ 54.217025] CPU0 CPU1
[ 54.222082] ---- ----
[ 54.227138] lock(&mgr->lock);
[ 54.230643] lock(&mgr->payload_lock);
[ 54.237742] lock(&mgr->lock);
[ 54.244062] lock(&mgr->payload_lock);
[ 54.248346]
[ 54.248346] *** DEADLOCK ***
[ 54.248346]
[ 54.254959] 7 locks held by kworker/1:6/1040:
[ 54.259822] #0: ffff888275c4f528 ((wq_completion)events){+.+.},
at: worker_thread+0x455/0x6e2
[ 54.269451] #1: ffffc9000119beb0
((work_completion)(&(&dev_priv->hotplug.hotplug_work)->work)){+.+.},
at: worker_thread+0x455/0x6e2
[ 54.282768] #2: ffff888272a403f0 (&dev->mode_config.mutex){+.+.},
at: i915_hotplug_work_func+0x4b/0x2be
[ 54.293368] #3: ffffffff824fc6c0 (drm_connector_list_iter){.+.+},
at: i915_hotplug_work_func+0x17e/0x2be
[ 54.304061] #4: ffffc9000119bc58 (crtc_ww_class_acquire){+.+.},
at: drm_helper_probe_detect_ctx+0x40/0xfd
[ 54.314855] #5: ffff888272a40470 (crtc_ww_class_mutex){+.+.}, at:
drm_modeset_lock+0x74/0xe2
[ 54.324385] #6: ffff888272af3060 (&mgr->lock){+.+.}, at:
drm_dp_mst_topology_mgr_set_mst+0x3c/0x2e4
[ 54.334597]
[ 54.334597] stack backtrace:
[ 54.339464] CPU: 1 PID: 1040 Comm: kworker/1:6 Not tainted
5.5.0-rc6-02274-g77381c23ee63 #47
[ 54.348893] Hardware name: Google Fizz/Fizz, BIOS
Google_Fizz.10139.39.0 01/04/2018
[ 54.357451] Workqueue: events i915_hotplug_work_func
[ 54.362995] Call Trace:
[ 54.365724] dump_stack+0x71/0x9c
[ 54.369427] check_noncircular+0x91/0xbc
[ 54.373809] ? __lock_acquire+0xc9e/0xf66
[ 54.378286] ? __lock_acquire+0xc9e/0xf66
[ 54.382763] ? lock_acquire+0x175/0x1ac
[ 54.387048] ? drm_dp_mst_topology_mgr_set_mst+0x218/0x2e4
[ 54.393177] ? __mutex_lock+0xc3/0x498
[ 54.397362] ? drm_dp_mst_topology_mgr_set_mst+0x218/0x2e4
[ 54.403492] ? drm_dp_mst_topology_mgr_set_mst+0x218/0x2e4
[ 54.409620] ? drm_dp_dpcd_access+0xd9/0x101
[ 54.414390] ? drm_dp_mst_topology_mgr_set_mst+0x218/0x2e4
[ 54.420517] ? drm_dp_mst_topology_mgr_set_mst+0x218/0x2e4
[ 54.426645] ? intel_digital_port_connected+0x34d/0x35c
[ 54.432482] ? intel_dp_detect+0x227/0x44e
[ 54.437056] ? ww_mutex_lock+0x49/0x9a
[ 54.441242] ? drm_helper_probe_detect_ctx+0x75/0xfd
[ 54.446789] ? intel_encoder_hotplug+0x4b/0x97
[ 54.451752] ? intel_ddi_hotplug+0x61/0x2e0
[ 54.456423] ? mark_held_locks+0x53/0x68
[ 54.460803] ? _raw_spin_unlock_irqrestore+0x3a/0x51
[ 54.466347] ? lockdep_hardirqs_on+0x187/0x1a4
[ 54.471310] ? drm_connector_list_iter_next+0x89/0x9a
[ 54.476953] ? i915_hotplug_work_func+0x206/0x2be
[ 54.482208] ? worker_thread+0x4d5/0x6e2
[ 54.486587] ? worker_thread+0x455/0x6e2
[ 54.490966] ? queue_work_on+0x64/0x64
[ 54.495151] ? kthread+0x1e9/0x1f1
[ 54.498946] ? queue_work_on+0x64/0x64
[ 54.503130] ? kthread_unpark+0x5e/0x5e
[ 54.507413] ? ret_from_fork+0x3a/0x50
The proper fix for this is probably cleanup the VCPI allocations when we're
enabling the topology, or on the first payload allocation. For now though,
let's just revert.
Signed-off-by: Lyude Paul <lyude@...hat.com>
Fixes: 64e62bdf04ab ("drm/dp_mst: Remove VCPI while disabling topology mgr")
Cc: Sean Paul <sean@...rly.run>
Cc: Wayne Lin <Wayne.Lin@....com>
---
drivers/gpu/drm/drm_dp_mst_topology.c | 13 -------------
1 file changed, 13 deletions(-)
diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 4b74193b89ce..0c585f2bbb69 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -3481,7 +3481,6 @@ static int drm_dp_get_vc_payload_bw(u8 dp_link_bw, u8 dp_link_count)
int drm_dp_mst_topology_mgr_set_mst(struct drm_dp_mst_topology_mgr *mgr, bool mst_state)
{
int ret = 0;
- int i = 0;
struct drm_dp_mst_branch *mstb = NULL;
mutex_lock(&mgr->lock);
@@ -3542,22 +3541,10 @@ int drm_dp_mst_topology_mgr_set_mst(struct drm_dp_mst_topology_mgr *mgr, bool ms
/* this can fail if the device is gone */
drm_dp_dpcd_writeb(mgr->aux, DP_MSTM_CTRL, 0);
ret = 0;
- mutex_lock(&mgr->payload_lock);
memset(mgr->payloads, 0, mgr->max_payloads * sizeof(struct drm_dp_payload));
mgr->payload_mask = 0;
set_bit(0, &mgr->payload_mask);
- for (i = 0; i < mgr->max_payloads; i++) {
- struct drm_dp_vcpi *vcpi = mgr->proposed_vcpis[i];
-
- if (vcpi) {
- vcpi->vcpi = 0;
- vcpi->num_slots = 0;
- }
- mgr->proposed_vcpis[i] = NULL;
- }
mgr->vcpi_mask = 0;
- mutex_unlock(&mgr->payload_lock);
-
mgr->payload_id_table_cleared = false;
}
--
2.24.1
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